JPWO2016027869A1 - Composite hollow fiber membrane module and manufacturing method thereof - Google Patents

Abstract

A forward osmotic composite hollow fiber membrane module having a hollow fiber bundle consisting of a plurality of hollow fibers, wherein the hollow fiber is provided with a separation active layer of a polymer thin film on the inner surface of a microporous hollow fiber support membrane A hollow fiber, the membrane area of the hollow fiber bundle is 1 m2 or more, and a method of measuring the mass of the separation active layer portion in a scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer The calculated module, wherein the calculated variation coefficient of the average thickness of the separation active layer in the radial direction and the length direction of the hollow fiber bundle is 0 to 60%.

Description

  The present invention relates to a composite hollow fiber membrane module and a method for producing the same. More specifically, the present invention relates to a composite hollow fiber membrane module having selective permeability used for removing a solid or solute from a liquid mixture and separating a solvent, and a method for producing the same. More specifically, a composite hollow fiber membrane module produced by forming a separation active layer composed of a polymer membrane having selective permeability on the inner surface of a microporous hollow fiber support membrane by a so-called interfacial polymerization method, And the manufacturing method.

As a method for producing purified water, forward osmosis technology is known (Patent Documents 1 and 2).
The forward osmosis technique is a method in which the raw water to be purified is brought into contact with an induction solution containing a high concentration of solute separable from water through a semipermeable membrane, and only the water in the raw water is extracted into the induction solution. It is a technique for obtaining purified water by removing solutes from the induction solution. In a water purification system that uses forward osmosis technology, the extraction of water from raw water into the induction solution is driven by the osmotic pressure difference, so it is not necessary to create an artificial pressure difference.
A composite membrane generally used as a forward osmosis membrane is produced by forming an active layer composed of a thin film on the surface of a support membrane. The active layer is formed by, for example, a coating method, an interfacial polymerization method, a plasma polymerization method, or the like.

In the interfacial polymerization method, two types of reactive monomers are dissolved in water and an organic solvent immiscible with water, and the solutions are brought into contact with each other to react the monomers at the interface between the two solutions to produce a polymer. It is. By performing this interfacial polymerization reaction on the surface of the microporous support membrane, a composite membrane used as a forward osmosis membrane can be obtained. Production of a composite film by a well-known interfacial polymerization method is performed as follows using two kinds of reactive compounds that can react with each other to form a polymer. Ie;
A first solution containing one reactive compound and a second solution containing the other reactive compound and immiscible with the first solution are prepared. And after immersing a microporous support membrane in the said 1st solution, after removing an excess 1st solution, it is immersed in a 2nd solution. Thereby, interfacial polymerization of the reactive compound is performed on the surface of the microporous support membrane. Thereafter, by removing the solvent of the second solution, a composite membrane having a thin film is formed on the surface of the microporous support membrane.

A method of forming a polymer thin film on the outer surface of a microporous support membrane having a hollow fiber shape by an interfacial polymerization method is well known. For example, a method is known in which a guide roll is provided in a reaction solution tank, and a microporous hollow fiber support membrane is continuously immersed in the reaction solution through this roll (Patent Documents 3, 4, etc.).
The technique of forming a polymer film on the outer surface of the hollow fiber has the advantage that it can be carried out continuously following the spinning process. However, this technique has a problem of damaging the polymer film formed by contact with a guide roll or contact between hollow fibers when filling a module.
On the other hand, when a polymer thin film is formed on the inner surface of the hollow fiber, it is possible to form the polymer film after modularizing the hollow fiber and damage the polymer film by subsequent handling. There is no.
As a method for forming the polymer thin film on the inner surface of the hollow fiber, for example, the hollow portion of the hollow fiber is filled with the first solution to form the liquid film of the first solution on the inner surface of the hollow fiber, and the excess solution is passed through the high-pressure air. A method of passing a second solution through the hollow portion after removal is known (Patent Document 5). Furthermore, a method of forming a polymer thin film on the inner surface of the hollow fiber by applying a prepolymer or an oligomer to the inner surface of the hollow fiber and then post-crosslinking is known (Patent Document 6).

Special table 2014-512951 gazette International Publication No. 2014/078415 JP 63-205108 A Japanese Patent Laid-Open No. 2-6848 Chinese Patent No. 101269301 Specification Japanese Patent Publication No. 3-35971

According to the technique of Patent Document 5, the following inconvenience occurs. Ie;
It is difficult to flow high-pressure air from the end face of the module at a uniform pressure over the entire area. Therefore, it is inevitable that there is a difference in the pressure of the passing air between the outer peripheral portion and the central portion in the radial direction of the module. As a result, a difference occurs in the thickness of the liquid film of the formed first solution, and thus a difference occurs in the thickness of the separation active layer formed of the polymer thin film to be formed. Also, the length direction of the module is formed because there is a difference in the thickness of the liquid film between the upper part of the module (upstream side of the air flow) and the lower part (downstream side) due to pressure loss when flowing high-pressure air. A difference occurs in the thickness of the separation active layer.
Further, the surface of the thin film formed by the technique of Patent Document 6 is extremely smooth, and therefore the water permeability is insufficient for practical use.

Thus, when a separation active layer made of a polymer thin film is formed on the inner surface of a hollow fiber by the conventional technique, only a composite hollow fiber module with uneven thickness can be obtained in both the radial direction and the length direction of the module. There is no. Such a module has a problem in that the desired performance cannot be exhibited, such as a large variation in water permeability from product to product or an increase in salt back diffusion.
The present invention has been made to improve the above-described present situation. Accordingly, an object of the present invention is to provide a composite hollow fiber membrane module having a separation active layer with little variation in average thickness in the radial direction and the length direction, and exhibiting stable high performance, and a method for producing the same. .

The present inventors have intensively studied to solve the above problems and completed the present invention.
The present invention is as follows.

[1] A forward osmotic composite hollow fiber membrane module having a hollow fiber bundle composed of a plurality of hollow fibers,
The hollow fiber is a hollow fiber provided with a separation active layer of a polymer thin film on the inner surface of a microporous hollow fiber support membrane,
The membrane area of the hollow fiber bundle was 1 m ² or more, and was calculated by a method of measuring the mass of the separation active layer portion in a scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer, The module according to claim 1, wherein a variation coefficient of an average thickness of the separation active layer in a radial direction and a length direction of the hollow fiber yarn bundle is 0 to 60%.
[2] In a scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer, the length L1 of the interface between the separation active layer and the hollow fiber support membrane, and the length L2 of the surface of the separation active layer The module according to [1], wherein the ratio L2 / L1 is 1.1 or more and 5.0 or less.

[3] The module according to [1] or [2], wherein the ratio L2 / L1 is 1.15 or more and 4.0 or less.
[4] The module according to [1] or [2], wherein the ratio L2 / L1 is 1.2 or more and 3.0 or less.

[5] The module according to any one of [1] to [4], wherein the coefficient of variation is 0 to 50%.
[6] The module according to any one of [1] to [4], wherein the coefficient of variation is 0 to 40%.
[7] The module according to any one of [1] to [4], wherein the coefficient of variation is 0 to 30%.

[8] The polymer is
At least one first monomer selected from polyfunctional amines;
At least one second monomer selected from the group consisting of a polyfunctional acid halide and a polyfunctional isocyanate;
The module according to any one of [1] to [7], which is a polycondensation product of
[9] The polymer is
The module according to [8], which is at least one selected from polyamide and polyurea.

[10] A method for manufacturing a module according to [8],
Forming a liquid membrane of a first solution containing one of the first monomer and the second monomer on the inner surface of the microporous hollow fiber support membrane;
Then, after providing a pressure difference so that the inner side and the outer side of the microporous hollow fiber support membrane are (inner pressure)> (outer pressure),
The method for producing the module, characterized by passing through a step of bringing a second solution containing the other of the first monomer and the second monomer into contact with a liquid film of the first solution.

[11] The method according to [10], wherein the pressure difference is generated by depressurizing the outside of the hollow fiber support membrane.
[12] The method according to [10], wherein the pressure difference is generated by pressurizing the inside of the hollow fiber support membrane.
[13] The method according to [10], wherein the pressure difference is generated by pressurizing both the outside and the inside of the hollow fiber support membrane with different pressures.
[14] The method according to any one of [10] to [13], wherein the pressure difference is 1 to 100 kPa.

  In the composite hollow fiber membrane module of the present invention, the average thickness of the separation active layer is uniform over the entire hollow fiber in the module and can be made thin, and the surface of the separation active layer has fine irregularities, Large surface area. Therefore, the water permeability is high, the back diffusion of the salt is small, and it has stable performance. Therefore, the composite hollow fiber membrane module can be suitably applied as a forward osmosis membrane. For example, in addition to seawater desalination, brackish water desalination, wastewater treatment, concentration of valuable materials, etc., oil and gas drilling It can also be suitably used for advanced treatment of accompanying water.

It is sectional drawing which shows an example of the structure of the composite hollow fiber membrane module of this invention. It is the schematic which shows an example of a structure of the apparatus which forms a separation active layer in a microporous hollow fiber support membrane module by the method of this invention. 2 is a scanning electron microscope image of a cross section of a hollow fiber of the module of Example 1. FIG. (A) is an outer periphery upper part, (b) is an outer periphery lower part, (c) is a center upper part, (d) is a cross-sectional image of the hollow fiber sampled from the center lower part. 4 is a scanning electron microscope image of a cross section of a hollow fiber of a module of Comparative Example 1. (E) is the outer periphery upper part, (f) is the outer periphery lower part, (g) is the center upper part, (h) is a cross-sectional image of the hollow fiber sampled from the center lower part. It is a scanning electron microscope image of the cross section of the microporous hollow fiber support membrane before interfacial polymerization. FIG. 4 is a drawing in which a portion corresponding to a separation active layer is emphasized in FIG. 3. FIG. 5 is a drawing in which a portion corresponding to the separation active layer is emphasized in FIG. 4. 10 is a scanning electron microscope image of a cross section of a hollow fiber of a module of Comparative Example 3. FIG. 9 is a diagram in which a portion corresponding to the separation active layer is drawn with emphasis in FIG. 8. In an Example, it is a reference figure which shows the collection position of the sample for scanning electron microscope image imaging | photography.

Hereinafter, an example of an embodiment of the present invention will be described in detail.
The forward osmotic composite hollow fiber membrane module of this embodiment has a hollow fiber bundle composed of a plurality of hollow fibers. Here, the hollow fiber is a hollow fiber in which a separation active layer of a polymer thin film is provided on the inner surface of a microporous hollow fiber support membrane, and the membrane area of the hollow fiber bundle is 1 m ² or more. From a practical viewpoint, it is preferably 1 m ² or more and 1,000 m ² or less.
In the forward osmosis composite hollow fiber membrane module of the present embodiment, the separation active layer formed on the inner surface of the hollow fiber support membrane is prevented from being damaged during contact with the guide roll, handling during module formation, or the like. First, it is preferable that the microporous hollow fiber support membrane is first modularized and then formed by forming a separation active layer inside the hollow fiber support membrane. By going through such a process, the formed isolation active layer can be prevented from being damaged.

The larger the water permeability of the forward osmosis composite hollow fiber membrane module of the present embodiment, the better. However, in order to secure a water permeability equivalent to or higher than that of a module having a space occupation volume equivalent to that of a commercially available membrane, a water permeability of 4 kg / (m ² × hr) or more is a guideline. Become. Further, the raw water to be treated, when the flow under conditions as possible without pressure loss, to avoid the risk of precipitation raw water depleted occurs, it is preferred that water permeation amount is 200kg / (m ² × hr) or less .
The water permeation amount of the composite hollow fiber module in the present specification is the amount of water that moves from the raw water to the induction solution due to osmotic pressure when the raw water to be treated with the forward osmosis membrane and the induction solution having a higher concentration are arranged. Which is defined by the following mathematical formula (1).
F = L / (M × H) (1)
Here, F is the amount of water permeated (kg / (m ² × hr)), L is the amount of permeated water (kg), M is the inner surface area (m ² ) of the membrane, and H is time (hr).

The reverse diffusion of the salt of the forward osmosis composite hollow fiber membrane module of the present embodiment is preferably as small as possible. Large salt back-diffusion results in contamination of raw water or leads to loss of induced solutes. From such a viewpoint, the reverse diffusion of the salt of the forward osmosis composite hollow fiber membrane module of the present embodiment is preferably 0.1% or less with respect to the value of the water permeability (kg / m ² / hr), 0.05% or less is more preferable, More preferably, it is 0.02% or less.
The reverse diffusion of the salt of the composite hollow fiber module in the present specification refers to the amount of salt transferred from the induction solution to the raw water when the raw water to be treated with the forward osmosis membrane interposed therebetween and the induction solution having a higher concentration than this are arranged. Which is defined by the following mathematical formula (2).
RSF = G / (M × H) (2)
Here, RSF is salt reverse diffusion (g / (m ² × hr), G is the amount of salt permeated (g), M is the membrane area (m ² ), and H is time (hr).

The said induction | guidance | derivation solution refers to the solution which shows a high osmotic pressure compared with the raw | natural water containing the substance to be separated, and has the function to move water from raw | natural water through a semipermeable membrane. This induction solution expresses a high osmotic pressure by containing the induction solute at a high concentration.
Examples of the induced solute include readily water-soluble salts such as sodium chloride, potassium chloride, sodium sulfate, sodium thiosulfate, sodium sulfite, ammonium chloride, ammonium sulfate, and ammonium carbonate;
Alcohols such as methanol, ethanol, 1-propanol, 2-propanol;
Glycols such as ethylene glycol and propylene glycol;
Polymers such as polyethylene oxide and propylene oxide;
Examples include copolymers of the above polymers.

The microporous hollow fiber support membrane in the present embodiment is a membrane for supporting the separation active layer composed of the polymer polymer thin film, and the membrane itself exhibits substantially separation performance with respect to the separation object. Preferably not. Any microporous hollow fiber support membrane including a known microporous hollow fiber support membrane can be used.
The microporous hollow fiber support membrane in the present embodiment preferably has micropores on its inner surface with a pore diameter of preferably 0.001 μm to 0.1 μm, more preferably 0.005 μm to 0.05 μm. . On the other hand, the structure up to the outer surface other than the inner surface of the microporous hollow fiber support membrane is preferably as sparse as possible as long as the strength is maintained in order to reduce the permeation resistance of the permeating fluid. The sparse structure of this part is preferably, for example, one of a net-like structure, a finger-like void, or a mixed structure thereof.

The permeation performance represented by the amount of pure water that permeates a certain membrane area (inner surface area) in a certain time when a certain pressure is applied to the microporous hollow fiber support membrane in this embodiment is preferably 100 kg / m. ² / hr / 100 kPa or more, more preferably 200 kg / m ² / hr / 100 kPa or more. If the permeation performance of the support membrane is too small, the permeation performance of the resulting composite hollow fiber membrane module tends to be small.
The permeation performance of the support membrane is preferably as large as possible without impairing the mechanical strength of the support membrane. In general, as the transmission performance increases, the mechanical strength decreases. Therefore, the transmission performance of the microporous hollow fiber support membranes in the present embodiment is preferably 50,000kg ^/ m 2 ^/ hr ^/ 100kPa or less, and more preferably less 10,000kg ^/ m 2 ^/ hr ^/ 100kPa as a guide .

  As a material for such a microporous hollow fiber support membrane, any material can be used as long as it can be formed on the microporous hollow fiber support membrane. However, in producing the composite membrane by the preferred production method in the present embodiment, it is necessary that it is not chemically damaged by the monomer solution used. Therefore, from the viewpoint of chemical resistance, film-forming property, durability, etc., as the material of the microporous hollow fiber support membrane, for example, polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polyamide, polyvinylidene fluoride, and The main component is preferably at least one selected from cellulose acetate, more preferably at least one selected from polysulfone and polyethersulfone, more preferably polyethersulfone.

  The yarn diameter size of the microporous hollow fiber support membrane used in this embodiment is not particularly limited, but considering the membrane formation stability, ease of handling, membrane area when modularized, etc., the outer diameter is 100 μm. Those having a diameter of ˜3,000 μm and an inner diameter of 30 μm to 2,500 μm are preferable, and the outer diameter is 200 μm to 1,500 μm, and the inner diameter is more preferably 50 μm to 1,000 μm. Such a microporous hollow fiber support membrane can be produced by a known dry / wet film formation method, melt film formation method, wet film formation method or the like using a material selected from the above materials.

The microporous hollow fiber support membrane module used in the present embodiment can be obtained by modularizing the microporous hollow fiber support membrane. As the module housing, a cylindrical housing having a diameter of 2 inches to 20 inches can be used, and for example, a module can be formed using an adhesive such as urethane or epoxy. The microporous hollow fiber support membrane has a structure in which a hollow fiber bundle is accommodated in a module and the end portion of the yarn bundle is fixed with the adhesive. Here, the adhesive is solidified so as not to block the holes of each hollow fiber. Thereby, the flowability of the hollow fiber can be ensured. Furthermore, the module communicates with the inside (hollow part) of the hollow fiber bundle, and does not communicate with the outside;
It is preferable to provide a conduit that communicates with the outside of the hollow fiber bundle and does not communicate with the inside. By adopting such a configuration, the inside and outside of the hollow fiber bundle can be placed under different pressures, and can be suitably used for forming a separation active layer in the present embodiment (described later). .
In the present embodiment, the separation active layer made of a polymer thin film has substantially separation performance that can be formed by an interfacial polymerization reaction.

The thickness of the polymer thin film is preferably as thin as there are no pinholes. However, in order to maintain mechanical strength and chemical resistance, an appropriate thickness must be provided. Therefore, in consideration of film-forming stability and permeation performance, the thickness of the polymer thin film is preferably 0.1 to 3 μm, more preferably 0.2 to 2 μm.
In the present embodiment, the membrane area is a value defined by the following mathematical formula (3) from the length, the inner diameter, and the number of hollow fibers excluding the bonded portion in the module. Here, a is the membrane area (m ² ), b is the length (m) of the hollow fiber excluding the bonded portion, c is the inner diameter (m) of the hollow fiber, and n is the number of hollow fibers.
a = c × π × b × n (3)
The membrane area of the module is preferably 1 m ² or more and more preferably 1.5 m ² or more from the viewpoint of practical use.

As the polymer in the polymer thin film, for example,
At least one first monomer selected from polyfunctional amines;
At least one second monomer selected from the group consisting of a polyfunctional acid halide and a polyfunctional isocyanate;
The polycondensation product is preferably. More specifically, for example, a polyamide obtained by interfacial polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide,
Examples thereof include polyurea obtained by an interfacial polymerization reaction between a polyfunctional amine and a polyfunctional isocyanate. The separation performance when these polymer thin films are used as the separation active layer refers to the performance of separating pure water from solutes such as ions dissolved therein.

  The type, combination, and type of solvent used (described later) of the first monomer and the second monomer may be any as long as both monomers immediately cause a polymerization reaction at the interface to form a polymer thin film. Is not particularly limited. However, it is preferable that at least one of the first monomer and the second monomer contains a reactive compound having three or more reactive groups. Since this forms a thin film made of a three-dimensional polymer, it is more preferable in terms of film strength.

  Examples of the other functional amines include polyfunctional aromatic amines, polyfunctional aliphatic amines, monomers having a plurality of reactive amino groups, and prepolymers thereof.

  The polyfunctional aromatic amine is an aromatic amino compound having two or more amino groups in one molecule, and more specifically, for example, m-phenylenediamine, p-phenylenediamine, 3,3 ′. -Diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylamine, 3,5-diaminobenzoic acid, 4,4'-diamino And diphenylsulfone, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 1,3,5, -triaminobenzene, 1,5-diaminonaphthalene, etc. Can be used. In the present invention, at least one selected from m-phenylenediamine and p-phenylenediamine is particularly preferably used.

The polyfunctional aliphatic amine is an aliphatic amino compound having two or more amino groups in one molecule. More specifically, for example, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, Cyclohexane rings such as 4,4′-bis (paraaminocyclohexyl) methane, 1,3-bis- (aminomethyl) cyclohexane, 2,4-bis- (aminomethyl) cyclohexane, 1,3,5, -triaminocyclohexane A primary amine with;
Secondary amines having a piperazine ring, such as piperazine, 2-methylpiperazine, ethylpiperazine, 2,5-dimethylpiperazine;
Secondary amines having a piperidine ring, such as 1,3-bis (4-piperidyl) methane, 1,3-bis (4-piperidyl) propane, 4,4′-bipiperidine;
Others such as amines with both primary and secondary amino groups, such as 4- (aminomethyl) piperidine;
Ethylenediamine, propylenediamine, 1,2-propanediamine, 1,2-diamino-2-methylpropane, 2,2-dimethyl-1,3-propanediamine, tris (2-aminoethyl) amine, N, N'- Examples thereof include dimethylethylenediamine and N, N′-dimethylpropanediamine, and these can be used alone or as a mixture thereof. Mixtures of these polyfunctional aliphatic amines and the above polyfunctional aromatic amines can also be used.

  Examples of the monomer having a plurality of reactive amino groups include polyethyleneimine, amine-modified polyepichlorohydrin, and aminated polystyrene. As the prepolymer, for example, a prepolymer composed of one or more selected from piperazine, 4- (aminomethyl) piperidine, ethylenediamine, and 1,2-diamino-2-methylpropane is preferably used.

  Examples of the polyfunctional halide include polyfunctional aromatic acid halides and polyfunctional aliphatic acid halides. These may be bifunctional or more so that they can react with the polyfunctional amine to form a polymer.

  The polyfunctional aromatic acid halide is an aromatic acid halide compound having two or more acid halide groups in one molecule. Specifically, for example, trimesic acid halide, trimellitic acid halide, isophthalic acid halide, terephthalic acid halide, pyromellitic acid halide, benzophenone tetracarboxylic acid halide, biphenyldicarboxylic acid halide, naphthalenedicarboxylic acid halide, pyridinedicarboxylic acid halide, benzene A disulfonic acid halide etc. can be mentioned, These can be used individually or in mixture. In the present embodiment, trimesic acid chloride alone, a mixture of trimesic acid chloride and isophthalic acid chloride, or a mixture of trimesic acid chloride and terephthalic acid chloride is preferably used.

The polyfunctional aliphatic acid halide is an aliphatic acid halide compound having two or more acid halide groups in one molecule. Specifically, cycloaliphatic polyfunctional acid halide compounds such as cyclobutane dicarboxylic acid halide, cyclopentane dicarboxylic acid halide, cyclopentane tricarboxylic acid halide, cyclopentane tetracarboxylic acid halide, cyclohexane dicarboxylic acid halide, cyclohexane tricarboxylic acid halide, etc. Etc .;
Examples thereof include propanetricarboxylic acid halide, butanetricarboxylic acid halide, pentanetricarboxylic acid halide, succinic acid halide, glutaric acid halide and the like. These can be used alone or as a mixture, and a mixture of these polyfunctional aliphatic halides and the above-mentioned polyfunctional aromatic acid halides can be used.

Examples of the polyfunctional isocyanate include ethylene diisocyanate, propylene diisocyanate, benzene diisocyanate, toluene diisocyanate, naphthalene diisocyanate, and methylenebis (4-phenylisocyanate).
The first monomer and the second monomer as described above are each subjected to interfacial polymerization as a solution obtained by dissolving them in an appropriate solvent.

In this specification,
The first solution refers to a solution containing a monomer that comes into contact with the microporous hollow fiber support membrane first,
The second solution refers to a solution containing a monomer that comes into contact with the support film after the first solution has contacted and reacts with the monomer in the first solution to form a polymer. One of the first monomer and the second monomer is contained in the first solution, and the other is contained in the second solution. Either monomer may be contained in either solution, but an embodiment in which both monomers are contained in one solution is not preferred.

As the solvent of the first solution and the solvent of the second solution, the monomers contained therein are dissolved, and when the two solutions are in contact, a liquid-liquid interface is formed and the microporous hollow fiber support membrane is not damaged. If there is no particular limitation. As such a solvent, for example, the solvent of the first solution may be water, alcohol alone or a mixture,
Examples of the solvent for the second solution include hydrocarbon solvents such as n-hexane, cyclohexane, n-heptane, n-octane, n-nonane, and n-decane, alone or as a mixture. By selecting the solvent as described above, the first solution and the second solution become immiscible, and the interfacial polymerization proceeds as expected.
Selecting the first monomer as the monomer contained in the first solution,
Selecting the second monomer as the monomer contained in the second volume liquid,
Each is preferred.
The concentration of these reactive compounds contained in the first solution and the second solution varies depending on the type of monomer, the partition coefficient with respect to the solvent, etc., and is not particularly limited. It should be set appropriately by those skilled in the art.

For example, an example in which an m-phenylenediamine aqueous solution is used as the first solution and an n-hexane solution of trimesic acid chloride is used as the second solution is as follows:
The concentration of m-phenylenediamine is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass. The concentration of trimesic acid chloride is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass. If the concentration of these solutions is too low, formation of a thin film by interfacial polymerization is incomplete and defects tend to occur, leading to a decrease in separation performance. On the other hand, if it is too high, the formed thin film becomes too thick, resulting in a decrease in permeation performance, and there is a possibility that the amount of residual unreacted material in the film increases and adversely affects the membrane performance.
When an acid is generated during the progress of the interfacial polymerization reaction, an alkali as an acid scavenger can be added to the first solution or the second solution. Moreover, you may add surfactant for improving the wettability with a microporous hollow fiber support membrane, the catalyst for accelerating | stimulating reaction, etc. as needed.

Examples of the acid scavenger include caustic alkalis such as sodium hydroxide;
Sodium phosphate such as trisodium phosphate;
Sodium carbonate such as sodium carbonate;
Examples thereof include tertiary amines such as trimethylamine, triethylamine, and triethylenediamine. Examples of the surfactant include sodium lauryl sulfonate and sodium lauryl benzene sulfonate. Examples of the catalyst include dimethylformamide. These can be previously contained in the first solution or the second solution.

An example of the structure of the hollow fiber membrane module in the present embodiment is shown in FIG.
The hollow fiber membrane module 1 has a structure in which a tubular body is filled with a yarn bundle composed of a plurality of hollow fibers 4, and both ends of the hollow fiber yarn bundle are fixed to a cylinder with adhesive fixing portions 5 and 6. . The cylindrical body has shell side conduits 2 and 3 on its side surface, and is sealed by headers 7 and 8. Here, each of the adhesive fixing portions 5 and 6 is solidified so as not to block the hole of the hollow fiber. Each of the headers 7 and 8 has core side conduits 9 and 10 that communicate with the inside (hollow portion) of the hollow fiber 4 and do not communicate with the outside. With these conduits, the liquid can be introduced into or taken out from the inside of the hollow fiber 4. The shell side conduits 9 and 10 communicate with the outside of the hollow fiber 4 and do not communicate with the inside.

In the present specification, the inner side of the hollow fiber is referred to as the core side, and the space between the outer side of the hollow fiber and the cylinder is referred to as the shell side. The hollow fiber membrane module in the present embodiment has a structure in which the liquid flowing on the core side and the liquid flowing on the shell side are in contact only via the hollow fiber membrane. Further, by applying different pressures to the shell side conduits 2 and 3 and the core side conduits 9 and 10, respectively, a pressure difference can be provided between the inside and the outside of the hollow fiber.
In the present embodiment, the core side of the microporous hollow fiber support membrane module is filled with the first solution containing one of the first monomer and the second monomer, and subsequently on the core side and the shell side. The microporous hollow fiber support membrane is provided by providing a pressure difference and then passing the second solution that contains the other of the first monomer and the second monomer and is immiscible with the first solution. The first monomer and the second monomer are reacted on the inner surface to form a polymer thin film, and the intended composite hollow fiber module is manufactured.

A method of providing a pressure difference between the core side and the shell side is arbitrary. For example, a method of depressurizing both the core side and the shell side;
Depressurizing the shell side and atmospheric pressure on the core side;
Pressurizing the core side with the shell side as atmospheric pressure;
Examples include a method of pressurizing both the core side and the shell side, and any method can be selected.
However, in the present embodiment, it is preferable to set the pressure on the shell side lower than the core side.

By providing the pressure difference as described above after filling the first solution on the core side (core-side pressure> shell-side pressure), excess first solution enters the micropores of the support membrane, and on the inner surface of the support membrane. It is considered that a thin film of the first solution having a relatively uniform thickness is formed throughout the module.
In this embodiment, the thickness of the separation active layer composed of a polymer thin film formed on the inner surface of the microporous hollow fiber support membrane of the composite hollow fiber module is closely related to the thickness of the liquid membrane of the first solution. doing. The thickness of the liquid film can be adjusted by the pressure difference between the core side and the shell side applied to the module, the time for maintaining the pressure difference, the amount of the surfactant added to the first solution, and the like.
As described above, the thickness of the separation active layer is preferably 0.1 to 3 μm, more preferably 0.2 to 2 μm. In order to form the separation active layer having this thickness, the pressure difference between the core side and the shell side is preferably 1 to 500 kPa, more preferably 5 to 300 kPa, and still more preferably 10 to 100 kPa. . The time for maintaining the pressure difference is preferably 1 to 100 minutes, more preferably 10 to 50 minutes. The addition amount of the surfactant added to the first solution is preferably 0.01 to 1% by mass and more preferably 0.05 to 0.5% by mass with respect to the total amount of the first solution.

The greater the pressure difference and the longer the time for maintaining the pressure difference, the thinner the liquid film of the first solution, and vice versa. If the thickness of the liquid film is too small, a portion where the liquid film is not formed occurs due to slight film thickness unevenness, causing a defect in the separation active layer. If the thickness of the liquid film is too large, sufficient permeation performance may not be obtained.
In the manufacturing method of the forward osmosis composite hollow fiber membrane module in the present embodiment, the pressure difference provided between the core side and the shell side is uniform from the outermost peripheral part to the center part of the hollow fiber in the module, and the hollow in the module Uniform from one end of the yarn to the other. As a result, the thickness of the liquid film of the first solution formed at each location becomes uniform, and the thickness of the polymer active layer formed based on the thickness becomes uniform. Therefore, the variation in the water permeation amount of the liquid in each part is reduced, and stable high performance can be exhibited as a composite hollow fiber membrane module.

  According to the prior art method of forming a liquid film of the first solution inside the hollow fiber through high-pressure air, the longer the module length and the larger the module diameter, the greater the separation at each of the above points. The variation in the average thickness of the active layer is increased. However, in the manufacturing method of the composite hollow fiber membrane module of this embodiment, it becomes substantially uniform at each location. The effect of the present invention becomes more prominent as the module size increases. However, practically, it is convenient to set the module length to 50 cm to 300 cm and the module diameter to 2 inches to 20 inches. Of course, the effect of the present invention is exhibited even when the module has a length and diameter less than or greater than this.

In the present invention, the variation in the average thickness of the separation active layer in each part of the hollow fiber membrane module in the composite hollow fiber module is represented by a coefficient of variation. The coefficient of variation is a value obtained by dividing the standard deviation of the values at each measurement point by the average value, and is expressed as a percentage (%). Each measurement point has an n number of 1 or more (n number of each portion) at each of the nine locations including the both ends and the central portion of the module at the three locations of the outer peripheral portion, the middle portion and the central portion in the radial direction of the module. Are the same).
The thickness at each measurement location is expressed as an average thickness in a measurement range of about 5 to 100 μm in length. The length of this measurement range is preferably 5 to 50 μm, more preferably 5 to 20 μm, and most preferably 13 μm. As will be described later, the separation active layer in the composite hollow fiber membrane module of the present embodiment preferably has a fine uneven shape on the surface thereof. Therefore, when evaluating the thickness of the separation active layer, it is appropriate to evaluate the average thickness of the measurement range at each measurement location. The separation active layer in the composite hollow fiber membrane module of the present embodiment has a small variation when comparing the average thickness measured at a plurality of measurement locations. The length direction of the measurement range in the average thickness evaluation may be the length direction of the hollow fiber, the circumferential direction of the hollow fiber, or the length direction of the hollow fiber. It may be an oblique direction. The direction of the length of the measurement range in the plurality of scanning electron microscope images used for calculating the average value may be the same or different from each other.

The variation rate of the average thickness of the separation active layer from the outermost periphery to the center of the hollow fiber in the composite hollow fiber membrane module in the present invention, and the separation active layer from one end of the hollow fiber in the module to the other end. The variation coefficient of the average thickness is preferably 0 to 60%, more preferably 0 to 50%, and further preferably 0 to 40%. Most preferably, it is 0 to 30%.
In the present invention, the thickness of the separation active layer is calculated by a method of measuring the mass of the separation active layer portion in a scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer. Specifically, a scanning electron microscope image of a hollow fiber cross section is printed, a portion corresponding to the separation active layer is cut out, its mass is measured, and an area is calculated using a calibration curve prepared in advance. The average thickness is calculated by the method.
The composite hollow fiber membrane module in the present embodiment has a small variation in the average thickness of the separation active layer at each location in the module. Therefore, the variation in performance from module to module is small and good. The performance referred to here is the water permeability and the back diffusion of salt.

  The separation active layer in the composite hollow fiber membrane module of the present embodiment has a large number of fine irregularities on its surface. The degree of unevenness on the surface of the separation active layer is determined based on the length L1 of the interface between the separation active layer and the hollow fiber support membrane in the scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer, and the separation activity. It can be estimated by the ratio L2 / L1 of the layer surface length L2. In the composite hollow fiber membrane module of the present embodiment, the ratio L2 / L1 in the cross-sectional image of the separation active layer is preferably 1.1 or more and 5.0 or less, more preferably 1.15 or less and 4.0 or less. More preferably, it is 1.2 or more and 3.0 or less. The ratio L2 / L1 can be evaluated using a scanning electron microscope image of a cross section of the hollow fiber membrane sample.

Hereinafter, an evaluation method of the ratio L2 / L1 will be described with reference to FIG. FIG. 6 is an image obtained by photographing a cross section of the hollow fiber in the composite hollow fiber membrane module obtained in Example 1 described later with a scanning electron microscope. FIG. 6A is a drawing in which a portion corresponding to the separation active layer is drawn with emphasis in a cross-sectional image of a hollow fiber sampled from the upper outer periphery of the module.
In FIG. 6A, the interface corresponding to the separation active layer and the hollow fiber support membrane, and the surface of the separation active layer are indicated by broken lines to emphasize the portion corresponding to the separation active layer. In this image, the length from the image left end to the right end of the interface between the separation active layer and the hollow fiber support membrane is L1, and the length from the image left end to the right end of the separation active layer surface is L2, respectively. The ratio L2 / L1 is calculated and used as an index of the surface roughness of the separation active layer.

For the calculation of the ratio L2 / L1, the magnification is such that all of the separation active layer in the thickness direction fits in one image within a range of 5,000 times to 30,000 times, and the length of the interface L1 A scanning electron microscope image set so that the ratio between the value and the average thickness of the separation active layer is 1.5 or more and 100 or less is used. The evaluation was performed by scanning electron microscope images taken for a total of nine samples taken from each end and center of the module at three locations, the outer peripheral portion, the middle portion, and the central portion in the radial direction of the module. The ratio L2 / L1 is obtained as an average value of the values calculated by using each. The length of L2 is measured for the separation active layer formed on the support film in the range corresponding to L1.
The direction of the line from the left end to the right end in the scanning electron microscope image used for the evaluation of the ratio L2 / L1 may be the length direction of the hollow fiber or the circumferential direction of the hollow fiber. The direction may be oblique with respect to the length direction of the hollow fiber. The directions of the lines from the left end to the right end in the plurality of scanning electron microscope images used for calculating the average value may be the same or different from each other.

The present inventors speculate as follows about the mechanism by which the surface of the separation active layer in the composite hollow fiber membrane module of the present embodiment has such a fine uneven shape. However, the present invention is not limited to the following theory.
The separation active layer in the composite hollow fiber membrane module of the present embodiment is preferably formed by interfacial polymerization. In the interfacial polymerization, when the liquid film of the first monomer solution formed on the surface of the hollow fiber comes into contact with the second monomer solution, it is considered that the polymerization proceeds at the interface without forming both, and a polymerization layer is formed. It is done. As a result, the formed separation active layer is considered to have a shape with many fine irregularities on the surface. If the separation active layer is formed by a method other than interfacial polymerization, it is not possible to form a separation active layer having a shape with many fine surface irregularities.

Hereinafter, a method for producing the composite hollow fiber membrane module of the present embodiment will be described with reference to FIG.
In the apparatus of FIG. 2, the microporous hollow fiber support membrane module 11 in which the inside of the microporous hollow fiber support membrane (core side) is filled with the first solution has a second solution storage tank 14 at the core side entrance. The pipe 16 is connected, and a pump 16 for pumping the second solution is connected on the way. A pipe 18 from the reaction waste liquid storage tank 17 is connected to the outlet on the core side, and the core side pressure adjusting device 12 for controlling the pressure inside the hollow fiber of the microporous hollow fiber support membrane module 11 from the tank. Are connected. An end cap 19 is fitted into the lower conduit on the shell side of the microporous hollow fiber support membrane module 11, and a shell side pressure adjusting device 13 for controlling the shell pressure is connected to the upper conduit.

Production of the composite hollow fiber membrane module in the present embodiment is performed, for example, according to the following procedure;
First, each pipe is connected to the microporous hollow fiber support membrane module 11 filled with the first solution on the core side (inside the microporous hollow fiber support membrane). Next, the core side pressure adjusting device 12 and the shell side pressure adjusting device 13 provide a pressure difference between the core side and the shell side (core side pressure> shell side pressure). At this time, the excess first solution in the hollow fiber on the core side enters the micropore due to the pressure difference (sometimes oozes up to the shell side), and a liquid film having a uniform thickness is formed inside the hollow fiber. The Next, the second solution in the storage tank 14 is sent to the inside of the hollow fiber by a pump and brought into contact with the liquid film of the first solution. By this contact, interfacial polymerization of both monomers occurs, and a separation active layer composed of a polymer thin film is formed inside the microporous hollow fiber support membrane. Here, when the second solution is fed, the pressure on the core side may fluctuate, but this pressure fluctuation is suppressed by the function of the core-side pressure control device 12.
Thus, when interfacial polymerization is performed, it is preferable to maintain a preset pressure difference between the core side and the shell side.

In this way, the polymer thin film is formed inside the microporous hollow fiber support membrane by interfacial polymerization of the first monomer and the second monomer, and the composite hollow fiber module of this embodiment is manufactured.
In the composite hollow fiber module of the present invention, the thickness of the liquid film of the first monomer solution for forming a polymer by interfacial polymerization is uniform between the outer peripheral portion and the central portion of the module, and the upper and lower portions of the module. Therefore, a uniform polymer layer is provided throughout the module. Since the above interfacial polymerization proceeds at the interface between the first monomer solution and the second monomer solution, the surface of the formed polymer layer has a shape with many fine irregularities.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited by an Example.

[experimental method]
(1) Production of microporous hollow fiber support membrane and hollow fiber membrane module Polyethersulfone (manufactured by BASF, trade name Ultrason) was dissolved in N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.). A 20% by weight hollow fiber spinning dope was prepared. A wet hollow fiber spinning machine equipped with a double spinning nozzle was filled with the above stock solution, extruded into a coagulation tank filled with water, and hollow fibers were formed by phase separation. The obtained hollow fiber was wound up on a winder. The hollow fiber thus obtained had an outer diameter of 1.0 mm, an inner diameter of 0.7 mm, a diameter of fine holes on the inner surface of 0.05 μm, and a water permeability of 1,020 kg / m ² / hr / 100 kPa.
This hollow fiber was used as a microporous hollow fiber support membrane.
An effective membrane having the structure shown in FIG. 1 by filling 1,500 microporous hollow fiber supporting membranes into a cylindrical plastic housing having a diameter of 5 cm and a length of 50 cm and fixing both ends with an adhesive. A microporous support membrane module having an inner surface area of 1.5 m ² was produced.
In the module of FIG. 1, the hollow portion of each hollow fiber passes through the adhesive fixing portions 5 and 6, and the hollow portion communicates with the core side conduits 9 and 10. On the other hand, the shell-side conduits 2 and 3 communicate with the space where the outside of the hollow fiber exists, but do not communicate with the hollow portion of the hollow fiber. Accordingly, by applying different pressures or reduced pressures to the core side conduits 9 and 10 and the shell side conduits 2 and 3, a pressure difference can be provided between the inside and the outside of the hollow fiber.

(2) Measurement of water permeability of composite hollow fiber membrane module and reverse diffusion of salt Pure water was added to the core side conduit (9 and 10 in FIG. 1) of the composite hollow fiber membrane module obtained in each Example and Comparative Example. A 50 L tank containing 30 L was connected by piping, and the pure water was circulated by a pump. The tank is equipped with a conductivity meter to measure the movement of salt into pure water. On the other hand, a 50 L tank containing 20 L of a saline solution having a concentration of 3.5% by mass was connected to the shell side conduit (2 and 3 in FIG. 1) by piping, and the saline solution was circulated by a pump. The tank on the core side and the tank on the shell side are each installed on a balance, and water movement can be measured. The core-side flow rate was 2.2 L / min and the shell-side flow rate was 8.8 L / min. Simultaneous operation was performed, and the amount of salt movement and the amount of water movement were measured. The amount of water permeation was calculated from the amount of water transferred, and the back diffusion of salt was calculated from the amount of salt transferred.

(3) Scanning electron microscope observation of separation active layer and measurement of average thickness The composite hollow fiber membrane module obtained in each Example and Comparative Example was disassembled, and the center in the radial direction of the module, the position of 50% of the radius And one hollow fiber was sampled from each of the three locations on the outermost periphery. Each hollow fiber was divided into 3 equal parts in the length direction to obtain 9 samples. Each of these hollow fiber samples was frozen and cut to prepare a hollow fiber cross-section sample.
Here, the sample preparation by freezing cleaving was performed as follows.
The hollow fiber was immersed in ethanol (Wako Pure Chemical Industries, Ltd.) and gelatin capsule No. After enclosing in 00 (manufactured by Wako Pure Chemical Industries, Ltd.), it is immersed in liquefied nitrogen for 5 minutes and frozen. For each frozen capsule, the hollow fiber is split using a scissors and a hammer. And the hollow fiber cross-section sample for scanning electron microscope observation was obtained by freeze-drying the obtained cut material.
Each of the cross-sectional samples was observed with a scanning electron microscope. The scanning electron microscopic observation was performed under the conditions of an acceleration voltage of 1.0 kV, a WD of 5 mm standard ± 0.7 mm, and an emission current setting of 10 ± 1 μA using a model S-4800 manufactured by Hitachi, Ltd. A microscopic image was printed on paper with a printer, the separated active layer portion was cut out, and the mass was measured with a precision balance. This mass was converted into the thickness (μm) of the separation active layer by a calibration curve prepared in advance. And the average value of nine samples was made into the average thickness of a separation active layer, and the standard deviation and the variation coefficient were computed.
Here, the length of the sample (image) subjected to mass measurement is a length corresponding to 13 μm in the circumferential direction for each sample (see FIG. 10).

(4) Measurement of ratio L2 / L1 In the scanning electron microscope image of the cross section of the hollow fiber obtained in (3) above, the length of the interface between the separation active layer and the hollow fiber support membrane was measured and set to L1. On the other hand, the length of the surface of the separation active layer (the membrane surface on the side not in contact with the hollow fiber support membrane) was measured and set to L2. Using these values, the ratio L2 / L1 was calculated.
The lengths of L1 and L2 were measured as follows.
A transparent double-sided tape was affixed to the measurement target portion of the scanning electron microscope image. Next, a wire was pasted from end to end of the image along each line (for example, a broken line in FIG. 6) of the interface and the surface, whose length was to be measured, and the remaining portion of the wire was cut. After that, the wire was peeled off and the length was measured. The wire used here is a 0.1 mmφ resin or metal wire that has negligible elasticity during use and is excellent in flexibility.

Example 1
In a 5 L container, 100 g of m-phenylenediamine and 8 g of sodium lauryl sulfate were added, and 4,892 g of pure water was further added and dissolved to prepare 5 kg of a first solution used for interfacial polymerization.
In another 5 L container, 8 g of trimesic acid chloride was added and 3,992 g of n-hexane was added and dissolved to prepare 4 kg of a second solution used for interfacial polymerization.
Filling the core side (inside the hollow fiber) of the microporous hollow fiber support membrane module with the first solution, leaving it for 30 minutes, draining the liquid, and the inside of the hollow fiber is wet with the first solution, It was mounted on the apparatus shown in FIG.
The core-side pressure adjusting device 12 set the core-side pressure to normal pressure, and the shell-side pressure adjusting device 13 set the shell-side pressure to 10 kPa as an absolute pressure. After standing in this state for 30 minutes, while maintaining this pressure, the second solution is fed to the core side at a flow rate of 1.5 L / min for 3 minutes by the second solution feed pump 16 to perform interfacial polymerization. It was. The polymerization temperature was 25 ° C.
Subsequently, the hollow fiber membrane module 11 was removed from the apparatus, and nitrogen at 50 ° C. was allowed to flow to the core side for 30 minutes to blow off n-hexane. Furthermore, the forward osmosis composite hollow fiber membrane module was produced by washing both the shell side and the core side with pure water.
The water permeability of this forward osmosis composite hollow fiber membrane module was 10.12 kg / (m ² × hr), and the back diffusion of the salt was 1.20 g / (m ² × hr).

Next, the above module was disassembled, hollow fibers were sampled from the above nine locations, and the average thickness of the separation active layer was measured. The results are shown in Table 1.
A scanning electron microscope image taken at this time is shown in FIG. (A) is an outer periphery upper part, (b) is an outer periphery lower part, (c) is a center upper part, (d) is a cross-sectional image of the hollow fiber sampled from the center lower part. FIG. 5 shows an image of a cross section of the microporous hollow fiber support membrane before the interfacial polymerization. Further, FIG. 6 shows a drawing in which a portion corresponding to the separation active layer is emphasized. FIGS. 6A to 6D are diagrams in which the portion corresponding to the separation active layer is emphasized with a broken line in the image of the same sign in FIG. Therefore, the broken lines in FIGS. 6A to 6D are cut lines when the mass of the separation active layer portion is measured in the above (3). The average thickness of each separation active layer calculated by the method described in (3) above was as follows:
(A) 1.43 μm, (b) 0.79 μm, (c) 0.68 μm, and (d) 0.63 μm
Furthermore, the values of the ratio L2 / L1 obtained by the method described in (4) above using the image of FIG. 6 were as follows:
(A) 1.46, (b) 1.33, (c) 1.25, and (d) 1.24

Example 2
A forward osmosis composite hollow fiber membrane module was produced in the same manner as in Example 1 except that the shell side pressure during the interfacial polymerization was changed to 50 kPa. The water permeability of this forward osmosis composite hollow fiber membrane module was 9.81 kg / (m ² × hr), and the back diffusion of the salt was 0.99 g / (m ² × hr).
Table 1 shows the result of the average thickness of the separated active layer measured by disassembling this module.

Example 3
A forward osmosis composite hollow fiber membrane module was produced in the same manner as in Example 1, except that the shell side pressure during the interfacial polymerization was 10 kPa, and the standing time after setting the pressure was 10 minutes. The water permeability of this forward osmosis composite hollow fiber membrane module was 9.73 kg / (m ² × hr), and the back diffusion of the salt was 1.13 g / (m ² × hr).
Table 1 shows the result of the average thickness of the separated active layer measured by disassembling this module.

Example 4
A forward osmosis composite hollow fiber membrane module was produced in the same manner as in Example 1 except that the core side pressure during the interfacial polymerization was 90 kPa and the shell side pressure was set to normal pressure. The water permeability of this forward osmosis composite hollow fiber membrane module was 10.89 kg / (m ² × hr), and the back diffusion of the salt was 1.47 g / (m ² × hr).
Table 1 shows the result of the average thickness of the separated active layer measured by disassembling this module.

Example 5
A forward osmosis composite hollow fiber membrane module was produced in the same manner as in Example 1 except that the core pressure during the interfacial polymerization was 190 kPa and the shell pressure was 100 kPa. The water permeability of this forward osmosis composite hollow fiber membrane module was 11.07 kg / (m ² × hr), and the back diffusion of the salt was 1.01 g / (m ² × hr).
Table 1 shows the result of the average thickness of the separated active layer measured by disassembling this module.

Comparative Example 1
In a 5 L container, 100 g of m-phenylenediamine and 7.9 g of sodium lauryl sulfate were added, and 4,892.1 g of pure water was further added and dissolved to prepare 5 kg of a first solution used for interfacial polymerization.
The second solution used for interfacial polymerization was prepared in the same manner as in Example 1.
The core side (inside the hollow fiber) of the microporous hollow fiber support membrane module was filled with the first solution, allowed to stand for 30 minutes, and then the liquid was drained to make the inside of the hollow fiber wet with the first solution. . Subsequently, the operation of passing high-pressure air through the core side at a pressure of 500 kPa for 0.5 seconds was repeated 20 times to remove excess first solution.
Thereafter, the second solution was fed to the core side of the module at a flow rate of 1.5 L / min for 3 minutes to perform interfacial polymerization. At this time, both the core side pressure and the shell side pressure were normal pressure, and the polymerization temperature was 25 ° C.
Next, 50 ° C. nitrogen is flowed to the core side of the module for 30 minutes to blow off n-hexane, and both the shell side and the core side are washed with pure water, thereby producing a forward osmosis composite hollow fiber membrane module. did.

By removing the composite hollow fiber support membrane module 11 from the apparatus, flowing nitrogen at 50 ° C. for 30 minutes to the core side to blow off n-hexane, and washing both the shell side and the core side with pure water. An osmotic composite hollow fiber membrane module was produced.
The water permeability of this forward osmosis composite hollow fiber membrane module was 5.53 kg / (m ² × hr), and the back diffusion of the salt was 30.2 g / (m ² × hr).
Table 1 shows the result of the average thickness of the separated active layer measured by disassembling this module.
A scanning electron microscope image taken at this time is shown in FIG. (E) is the outer periphery upper part, (f) is the outer periphery lower part, (g) is the center upper part, (h) is a cross-sectional image of the hollow fiber sampled from the center lower part. Further, FIG. 7 shows a drawing in which a portion corresponding to the separation active layer is emphasized. FIGS. 7E to 7H are diagrams in which the portion corresponding to the separation active layer in the image having the same sign in FIG. 4 is highlighted with a broken line. Therefore, the broken lines in FIGS. 7E to 7H are cut lines when the mass of the separation active layer portion is measured in the above (3). The average thickness of each separation active layer was as follows:
(E) 2.37 μm, (f) 1.76 μm, (g) 4.65 μm, and (h) 0.38 μm

  As can be seen from Table 1, the composite hollow fiber membrane module of this embodiment is good in that the average thickness of the separation active layer is small compared to the prior art module manufactured using high-pressure air.

Example 6
In this example, the variation in performance of the forward osmosis composite hollow fiber membrane module produced in the same manner as in Example 1 was examined.
By repeating the operation of Example 1, five forward osmosis composite hollow fiber membrane modules including the module of Example 1 and the same production method were produced.
Table 2 shows the water permeability of each module, the average value, the standard deviation, and the coefficient of variation, and the results of the salt reverse diffusion measurement of each module.
Comparative Example 2
The variation in performance was examined in the same manner as in Example 6 except that the method for producing the module was changed to the method of Comparative Example 1.
By repeating the operation of Comparative Example 1, five forward osmotic composite hollow fiber membrane modules including the module of Comparative Example 1 and the same production method were produced, and the performance of each was examined. The results are shown in Table 2.

  As is clear from Table 2, the composite hollow fiber membrane module of the present embodiment has a large water permeability and a small variation. Further, the back diffusion of the salt is small, and good performance can be stably exhibited.

Comparative Example 3
100 parts by mass of aromatic polysulfone (trade name: Udel Polysulfone P-1700, manufactured by Union Carbide) and 100 parts by mass of polyvinylpyrrolidone K90 (manufactured by Wako Pure Chemical Industries, Ltd.) were added to dimethylformamide (Wako Pure Chemical Industries, Ltd.). The mixture was dissolved in 500 parts by mass of (made) and sufficiently degassed to obtain a polymer solution. Next, 3 ml of the obtained polymer solution was dropped on a glass plate having a size of 10 cm × 10 cm and a thickness of 3 mm, cast with a doctor blade having a width of 50 mm and a gap of 100 μm, and then heated with 80 ° C. hot air for 2 hours. By removing the solvent, a non-porous flat membrane substrate having a film thickness of 30 μm was obtained, in which 100 parts by mass of aromatic polysulfone and 100 parts by mass of polyvinyl pyrrolidone K90 were extremely uniformly mixed.
On the other hand, a room temperature curing type silicone rubber (trade name: Silpot 184W / C, manufactured by Dow Corning) and a 1/10 mass curing catalyst thereof are dissolved in n-pentane to obtain a 1 mass% silicone solution. Prepared.
After the silicone solution obtained above is supplied to the surface of the non-porous flat membrane substrate at a supply rate of about 30 ml / min for about 3 minutes, air is passed at a linear speed of 30 m / sec for about 1 minute. It was. Then, after performing a crosslinking treatment by heating at 100 ° C. × 1 Hr, the surface of the porous flat membrane substrate made of aromatic polysulfone is immersed in ethanol at 60 ° C. for 16 hours to extract and remove polyvinylpyrrolidone. Further, a composite separation membrane formed by forming a silicone rubber thin film was obtained. This silicone rubber thin film has very little thickness unevenness and does not substantially penetrate into the pores of the substrate surface.
About the obtained composite separation membrane, ratio L2 / L1 calculated | required by the method as described in said (4) was 1.01. Scanning electron microscope images of the composite separation membrane used for calculating the ratio L2 / L1 are shown in FIGS.
The results are shown in Table 3 together with the result of the ratio L2 / L1 in Example 1.

As is apparent from Table 3, in Example 1 where the formation of the separation active layer was performed by interfacial polymerization, a separation active layer having a lot of surface micro unevenness was obtained.
In Comparative Example 3 in which the formation of the separation active layer was performed by a polymer solution coating method, the obtained separation active layer had few surface micro unevennesses.

  The composite hollow fiber module of the present invention is suitably used as a forward osmosis membrane, for example, for desalination of seawater, desalination of brine, drainage treatment, concentration of various valuable materials, advanced treatment of associated water in oil and gas drilling, etc. It is done.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module 2, 3 Shell side conduit | pipe 4 Hollow fiber 5, 6 Adhesive fixing | fixed part 7, 8 Header 9,10 Core side conduit | pipe 11 Hollow fiber membrane module 12 Core side pressure regulator 13 Shell side pressure regulator 14 14th 2 solution storage tank 15 2nd solution feed pipe 16 2nd solution feed pump 17 2nd solution drain tank 18 2nd solution drain pipe 19 End cap

Claims (14)

A forward osmotic composite hollow fiber membrane module having a hollow fiber bundle composed of a plurality of hollow fibers,
The hollow fiber is a hollow fiber provided with a separation active layer of a polymer thin film on the inner surface of a microporous hollow fiber support membrane,
The membrane area of the hollow fiber bundle was 1 m ² or more, and was calculated by a method of measuring the mass of the separation active layer portion in a scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer, The module according to claim 1, wherein a variation coefficient of an average thickness of the separation active layer in a radial direction and a length direction of the hollow fiber yarn bundle is 0 to 60%.   In the scanning electron microscope image obtained by photographing a cross section in the thickness direction of the separation active layer, the ratio L2 / the length L1 of the interface between the separation active layer and the hollow fiber support membrane, and the length L2 of the surface of the separation active layer The module according to claim 1, wherein L1 is 1.1 or more and 5.0 or less.   The module according to claim 1 or 2, wherein the ratio L2 / L1 is 1.15 or more and 4.0 or less.   The module according to claim 1 or 2, wherein the ratio L2 / L1 is 1.2 or more and 3.0 or less.   The module according to any one of claims 1 to 4, wherein the coefficient of variation is 0 to 50%.   The module according to any one of claims 1 to 4, wherein the coefficient of variation is 0 to 40%.   The module according to any one of claims 1 to 4, wherein the coefficient of variation is 0 to 30%. The polymer is
At least one first monomer selected from polyfunctional amines;
At least one second monomer selected from the group consisting of a polyfunctional acid halide and a polyfunctional isocyanate;
The module according to claim 1, which is a polycondensation product of The polymer is
The module according to claim 8, which is at least one selected from polyamide and polyurea. A method of manufacturing a module according to claim 8,
Forming a liquid membrane of a first solution containing one of the first monomer and the second monomer on the inner surface of the microporous hollow fiber support membrane;
Then, after providing a pressure difference so that the inner side and the outer side of the microporous hollow fiber support membrane are (inner pressure)> (outer pressure),
The method for producing the module, characterized by passing through a step of bringing a second solution containing the other of the first monomer and the second monomer into contact with a liquid film of the first solution.   The method according to claim 10, wherein the pressure difference is generated by depressurizing the outside of the hollow fiber support membrane.   The method according to claim 10, wherein the pressure difference is generated by applying pressure inside the hollow fiber support membrane.   The method according to claim 10, wherein the pressure difference is generated by pressurizing both the outside and the inside of the hollow fiber support membrane with different pressures.   The method according to any one of claims 10 to 13, wherein the pressure difference is 1 to 100 kPa.